Catheter Device

ABSTRACT

A catheter device having a shaft that extends from a proximal end to a distal end to carry on its distal end a self-expanding implant for intraluminal advance on a guidewire and delivery of the implant to an implant site by proximal withdrawal of CD a sheath that lies radially outside the implant in the catheter, the catheter including a first shaft element to pull the sheath proximally and a second shaft element to push the implant distally to prevent the implant moving proximally with the sheath when the sheath is pulled proximally, wherein the second shaft element comprises a pusher-guider tube having a wall thickness with a plurality of discrete slits, the slits extending through the wall thickness of the pusher-guider tube.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a catheter device having a shaft, arapid-exchange guidewire lumen (one which terminates at a proximalguidewire exit port that is distal of the proximal end of the catheter)and a distal end which exhibits a sheath which can be withdrawnproximally to release a self-expanding implant such as a stent. Toprevent the self-expanding stent moving proximally with theproximally-moving sheath, the catheter device includes a stopper whichbears on the stent and resists its proximal movement.

2. Background Prior Art

Conventionally, such a catheter device exhibits a shaft comprising anouter tube connected to the sheath and an inner shaft connected to thestopper, whereby the proximal movement of the sheath is accomplished byimposing an endwise tension on the outer tube, with the inner shaftcarrying an endwise compression stress, as the stopper at the distal endof the inner shaft works to resist proximal movement of the stent. Forexamples, see WO 03/003944, WO 03/002020, WO2004/062458 andEP-A-1095634.

Such conventional systems can work well, and can be of relatively simpleconstruction. However, the present inventor has discovered that they arenevertheless capable of improvement.

One disadvantage noted by the present inventor is that release of thestent requires the medical practitioner to maintain the inner pushershaft unchanged in axial disposition relative to the site of stenting inthe body of the patient, while pulling back on the outer tube of theshaft to release the stent. This pulling back of the outer tube requiresrelative movement of the outer tube in the bodily lumen (or guidecatheter) in which it has been advanced to the site of stenting. Anyfriction or resistance to axial movement of the outer tube in the lumenin which it is located hinders the objective of maintaining the stopperin a precise disposition relative to the target stenting site. Inpractice, it is customary to compensate for axial strain in knownsystems by positioning the stent slightly distal of the desired endposition before commencing stent deployment by pulling back the sleeve.The present invention is useful in reducing or eliminating the need forsuch compensation.

SUMMARY

The present invention is an improvement of the invention disclosed inWO-A-2005/053574.

It is an object of the present invention to improve the deploymentcapabilities of the catheter-based implant delivery system to a targetimplant site in a human or animal body. These deployment capabilitiesare particularly important, when the implant is intraluminally advancedalong a tortuous path through the system of body vessels. It is anotherobject of the present invention to improve the capability of thedelivery system to accurately release the implant at the implant site byproximal withdrawal of the sheath radially surrounding the implant.

These objects are solved by a feature combination of claim 1. Preferred,or optional features are the subject of the dependent claims.

The invention provides a catheter device in which a second shaft elementfor pushing the implant distally to prevent the implant from movingproximally with a sheath constraining the implant in a radiallycompressed delivery configuration inside the sheath of the catheterdevice comprises a pusher-guider tube having a wall thickness with aplurality of discrete slits that extend through the wall thickness ofthe pusher-guider tube. The slits render the pusher-guider tube morebendable than a tube without slits, but without prejudice to the abilityof the pusher-guider tube to prevent the implant from moving proximallywith the implant. The improved bendability has the effect that thesteering capabilities of the catheter device are improved.

Furthermore, the slits are arranged such that axial bendability of thepusher-guider tube is improved, yet torqueability is maintained so thatmanoeuvrability of the catheter device by the medical practitioner isnot compromised. Moreover, the improved bendability of the distalportion of the pusher-guider tube enables the pusher-guider tube to bemade preferably of metal, thus adding to the metal modular structure ofthe catheter device.

Moreover, the catheter device of the present invention comprises astopper for abutting the implant when proximally withdrawing the outersheath. The arrangement of slits can be confined to the portion of thepusher-guider tube distal to the stopper. Thus, bendability of theportion distal to the stopper is increased so that the bendabilitycapabilities of the catheter device distal to the stopper are determinedby the bendability of the implant, that is to say the portion of thepusher-guider tube distal to the stopper has very little adverse effecton the overall bendability in the section of the catheter distal to thestopper. Where the portion of the pusher-guider tube distal to thestopper only serves the purpose of facilitating the insertion of theguidewire through the distal tip of the catheter, this portion needs nosubstantial mechanical strength for pushing, pulling or twisting anycomponent of the catheter system.

In another embodiment of the present invention, the portion of thepusher-guider tube proximal of the stopper has been subjected to a heattreatment process, such as annealing, which is selected to yield adesired stiffness or bendability of the pusher-guider tube in the regionproximal of the stopper, and the torqueability required and the abilityto accommodate axially compressive when the stopper presses on theimplant during proximal withdrawal of the sheath.

In accordance with the disclosure of WO-A-2005/053574, the presentinvention is useful in improving positional placement of aself-expanding stent at a target stenting site in a human or animalbody, when using a transluminal, catheter-based stent delivery system. Acatheter device of the type identified above is provided, and in whichthe shaft of the catheter device features a shaft pusher tube with alumen and with a distal end operatively connected to the stent stopper,the lumen of the pusher tube being occupied by a pull wire or rod whichis arranged to pull back the sheath surrounding the self-expandingstent. The wire or rod can itself be tubular. It is resistant to endwiseextension of its length, and the pusher tube is resistant to endwiseshortening of length when placed in endwise compression. Normally, bothso-axial elements will be of a suitable metal such as stainless steel.

The present invention can be useful in a method of deploying aself-expanding stent in which a sheath surrounding the stent is pulledback proximally by a pull wire within the shaft of a rapid-exchangetransluminal catheter delivery system for the stent.

It will be appreciated that, with an arrangement in accordance with thepresent invention, there is no requirement for any axial movement of theouter shaft tube relative to the lumen in which it slides. The lumencould be that of a human or animal body, or that of a catheter such as aguide catheter, lying within such a bodily lumen. Instead, since theshaft tube is connected to the stent stopper, it is required that therebe no such axial movement during release of the prosthesis. Accordingly,any binding between the shaft tube and any surrounding guide catheter,or bodily tissue of the access lumen, and any friction acting on theoutside surface of the shaft tube, is turned by the present inventioninto an advantage rather than a problem, because it will help to confirmthe axial position of the shaft tube relative to the stopper and thestenting site. The more tortuous the access lumen in the body, the morelikely it is that during release of the stent there will be no axialmovement of the shaft tube and stopper relative to the intended stentingsite.

Furthermore, a shaft tube has more inherent resistance to elastic axialcompression no other end-to-end shortening than a mere wire within thelumen of the tube. Thus, regardless how great are the tensile stressesimposed on the pull wire during the push-pull activity of stent release,there should be less unwanted proximal movement of the stopper from theintended site of stenting. The shaft tube may be of stainless steel orof a cobalt/chromium/nickel alloy sold under the trademark PHYNOX.

Furthermore, the sheath itself can also, be metal-reinforced (such as byan embedded metal braid) and so also with a high capacity to resistaxial strain, increasing the precision with which the operator of thecatheter device can control the progressive withdrawal of the sheath andrelease of the stent. Many doctors prefer to release a self-expandingstent in a step-wise movement. If the pulling system stretches, then astep-wise movement can have the consequence of a time-dependent responseat the distal end of the system, and a relaxation of the pulling systembetween successive pulling steps, with consequent undesirable reversedistal movement of the sheath or else “lost movement” in the pullingsystem as it once again strains to take up the pull tension withsuccessive step-wise pulls at the proximal end of the system.

Thus, the shaft tube is conveniently a stainless steel or PHYNOXhypotube and the pull wire is conveniently of metal, such as a stainlesssteel wire, either Solid or hollow. While the sheath will very likely beof polymer, it can be made resistant to elastic stretching duringproximal withdrawal and release of the stent by embedding within theannular wall thickness of the polymer sheath a fiber reinforcement suchas a braided metal mesh. Here, there is effectively a continuous strandof elastic strain-resistant metal in the pulling system, all the wayfrom the proximal end of the pull wire to the distal end of the polymersheath, again adding to the precision of proximal withdrawal, andminimising any elastic strain within the system during withdrawal.

The pull wire can be connected to the sheath by, for example, first andsecond metal rings, one inside the other, and sandwiching the sheath sothat one of the metal rings is inside the sheath annulus and the otheris outside the sheath annulus. The inside metal ring would normally bewelded, soldered or brazed to the distal end of the pull wire (adhesivesbeing generally disfavoured in failure-critical applications in suchstent delivery devices) while the outer metal ring can be swaged downonto the sheath to press the sheath radially inwardly to a radius lessthan that of the outer diameter of the inside metal ring.

The present applicant has developed stent delivery systems (seeWO2001/34061) which feature a catheter system having a heat-formedtapered distal tip which can help to reduce trauma to the body as thecatheter system is advanced in a bodily lumen along its guidewire.Preferably the sheath has a tapered distal tip, which can beheat-formed, and which desirably tapers down to an end orifice whichfits relatively closely around the cylindrical outside surface of theguidewire.

The catheter shaft diameter may be defined by the pusher tube, and issmaller than the diameter of the sheath around the stent. At theproximal end of the sheath, it may be attractive to taper the diameterdown to a relatively snug fit around the outside of the shaft tube (butnot so snug as to resist proximal axial sliding of the sheath along theoutside of the shaft tube). It is contemplated to create the proximalguidewire exit port in the tapered proximal end of such a formed sheath,as explained below in more detail in relation to the accompanyingdrawings.

The proximal end of the sheath can be joined to a metal collar thatdefines a proximal guidewire exit port lumen and another lumen toslidably receive the outer tube of the catheter shaft. The collar can begiven a domed shape facing proximally, to facilitate atraumaticwithdrawal of the catheter system.

One way of connecting the shaft tube to the stopper is by way of apusher-guider tube which defines a guidewire lumen and carries thestopper at a location near the distal end of the pusher-guider tube, orat its distal end. The proximal end of the pusher-guider tube isarranged to one side of the distal end of the shaft tube and fixedrelative to it, such as by welding or gluing. Conveniently, both thepusher-guider tube and the shaft tube are of metal such as stainlesssteel, simplifying the task of bonding together side-by-side theproximal end of the pusher tube and the distal end of the shaft tube, asby welding or brazing. Other means of joining these tube sections willbe apparent to those readers skilled in the field, who will alsoappreciate that adhesive compositions are generally disfavoured,whenever failure of the adhesive bond results in failure of the deviceand risk to the patient, in use.

Distal of the stopper, the pusher-guider tube is not required to carryany substantial axial compressive stress. In any event, it should besoft and easily bendable so as to keep the catheter tip as floppy aspossible. The compression resistant pusher-guider tube could be extendeddistally beyond the stopper, all the way to the distal end of thesheath, in order to define a guidewire lumen which extends within thepusher tube all the way to the distal end of the system. Indeed, thepusher tube could extend into an atraumatic tip distal of the distal endof the sheath. In this way, the tapered tip of the sheath could beomitted.

Thus, there can be provided, distal of the stopper, a pusher tubeextension, which continues the guidewire lumen from the stopper to thedistal end of the system, but which may be of less heavy construction,being formed for example of thin wall polymer tube. Another usefulpurpose of such a guidewire lumen distal of the stopper is for carryinga radiopaque marker band to indicate the distal end of the stent withinthe delivery system, so that the radiologist can determine withprecision where the stent in the delivery system is located relative tothe target stenting site.

For the sake of completeness, and to put the present invention in thecontext of the prior art documents seen with hindsight to be helpful inappreciating how the present invention contributes to the state of theart, reference will now be made to EP-A-611 556 and WO 96/39998.

EP-A-611 556 discloses a rapid exchange balloon catheter stent deliverysystem in which a sheath is pulled back proximally by a pull wire, toexpose a stent mounted on a balloon, so that the stent can then bedeployed by inflation of the balloon. The stent is not a self-expandingstent, so is not pressing on the luminal surface of the sheath duringadvance of the delivery system to bring the stent into the location ofstenting. Accordingly, the balloon-expandable stent is not liable to becarried proximally by the sheath when the sheath is pulled proximally.Accordingly, there is no need for a stopper to resist unwanted proximalmovement of the stent. Accordingly, there is no significant resistanceto proximal movement of the sheath. Accordingly, there is no need forthe shaft of the system, defining the lumen in which the pull wire islocated, to be resistant to axial compressive stresses. The problem ofdesigning a system to deliver a self-expanding stent which maintains theaxial position of the stent correct during stepwise release of the stentis not a problem experienced with balloon-expandable stent deliverysystems.

Conversely, WO 96/39998 is a disclosure which is concerned with systemswhich will resist endwise compression during delivery of aself-expanding stent and proximal withdrawal of a sheath surroundingsuch a stent. The problem is addressed by providing within the deliverysystem an inner core which is resistant to endwise compression, andproviding a stopper near the distal end of the inner core. Thus, thepull wire is not housed within the lumen of the element that is inendwise compression during stent release but instead, is lyingside-by-side with the element that is subject to endwise compression.Any capability that the outer sheath of the system might have to carryendwise compression stress remains unutilised.

Examples in the state of the art of the use of a slit to increaseflexibility of a metal tube are to be found in, for example,EP-A-1103281 and JP-A-2002 301161 Terumo. For a better understanding ofthe present invention, and to show more clearly how the same may becarried into effect, reference will now be made, by way of example, tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal diametrical section through the distal end zoneof a catheter device;

FIG. 2 is the identical section, at larger scale, through the distalpart of the distal zone of FIG. 1;

FIG. 2A is a section, at a larger scale, through a distal part of adistal zone of a catheter device according to the present invention;

FIG. 3 is an identical section, at larger scale, through the proximalpart of the distal zone of FIG. 1; and

FIG. 4 is a longitudinal diametrical section, at enlarged scale, of thejunction between the pusher tube and pusher tube extension of FIG. 1.

FIG. 5 is a view from the side of a catheter-based delivery system;

FIG. 6 is a longitudinal diametrical section through the distal end ofthe catheter-based delivery system of FIG. 5;

FIG. 7 is an isometric view of the adaptor block of FIG. 6

FIG. 8 is a longitudinal diametrical section through a shaft portion ofthe catheter-based delivery system, including a guider block

FIG. 9 is an isometric view of the guider block of FIG. 8

FIG. 10 is a transverse section through the guider block, on the lineX-X in FIG. 8

FIG. 11 is a longitudinal diametrical section through the proximal partof the shaft of the catheter-based delivery system

FIGS. 12 and 13 are sections through two alternative proximal ends ofthe pull wire of the catheter-based delivery system, and

FIG. 14 is a longitudinal medial section through the hand unit of thecatheter-based delivery system.

DETAILED DESCRIPTION

Referring to FIGS. 1, 2 and 3 which form part of the invention describedin WO-A-2005/053574, a self-expanding stent 10, or stent graft, liesinside the distal end zone 12 of a sheath 14 with a tapered distal tip16 and a heat-formed proximal end 18 which defines the orifice 20 of aproximal guidewire exit port for a guidewire 22. Being a self-expander,the stent 10 is, at least at body temperature, putting compressivestress on the luminal surface of the sleeve 14 in the distal end zone12. Proximal of the stent 10, and on the abluminal surface 24 of thesleeve 14, is a swaged marker band 26 of radiopaque metallic material,which is pressing radially inwardly the material of the sheath 14 withinthe band 26. Radially inside the sheath at this point is a stepped metalannulus 28 which is itself put under radially inwardly compressivestress by the material 30 of the sheath 14 inside the marker band 26.Thus, the sheath material 30 is compressed between metal bands inside(28) and outside (26) the sheath 14. Brazed to the annulus 28 is a pullwire 32 which runs from the annulus 28 all the way back to the proximalend of the catheter device, whereby endwise tensile stress imposed onthe proximal end of the pull wire 32 will pull proximally the annulus 28and thereby impose on portions of the sheath 14 distal of the annulus 28an endwise tensile stress, for pulling the sheath 14 proximally withrespect to the stent, to release the stent. At the same time, portionsof the sheath 14 proximal of the annulus 28 will be pushed proximally.

A pusher annulus 40 is located in the lumen of the sheath 14 justproximal of the stent 10. Its purpose is to resist proximal movement ofthe stent 10, when the sheath 14 is withdrawn proximally from the stent10. It can also serve as a radiopaque marker band to indicate theproximal end of the stent 10. The pusher annulus 40 is brazed or weldedor otherwise fixed to a pusher-guider tube 42 which is conveniently ofstainless steel or PHYNOX™ and which has its distal end 44 distal of thepusher annulus 40 and within the lumen of the stent 10. The proximal end46 of the pusher tube 42 is arranged side-by-side with the distal end 50of a shaft pusher tube 52 of the catheter device which extends all theway to the proximal end of the catheter device and is convenientlyprovided as a PHYNOX or stainless steel hypo tube. The lumen of thisshaft tube 52 carries the pull wire 32. The overlapping portions 46 and50 of the pusher-guider tube and shaft pusher tube are bonded to eachother, conveniently by brazing, so that they effectively form a singlemetal strand from the proximal end of the catheter device to the stentpusher annulus 40. As can be seen in FIG. 1 and FIG. 3, the end orifice54 of the pusher tube 42 is co-linear with the orifice 56 in theheat-formed end 18 of the sheath 14, which defines the proximalguidewire exit lumen. Thus, when a guidewire 22 is advanced through theguidewire lumen of the catheter device by introducing it into the endorifice 58 of the tapered distal tip 16 of the sheath 14, the end of theguidewire will advance proximally along the pusher tube and exit throughthe port 56.

A particular embodiment of the present invention is described in FIG. 2Awhich is an improvement of the invention described in WO-A-2005/053574.It is obvious for the skilled person that parts of the disclosure ofWO-A-2005/053574 also apply to what is shown in FIG. 2A.

With reference to FIG. 2A, proximal of the stent (not shown), and on theabluminal surface 24 of the sleeve 14, are swaged steel bands 26A, 26B,which are pressing the material of the sheath 14 enclosed by the bands26A, 26B radially inwardly. Radially inside the sheath andlongitudinally between the two bands 26 a, 26 b is a metal annulus 28.The metal annulus 28 is welded to a pull wire 32. The location at whichthe annulus 28 is welded to the pull wire 32 is indicated by referencenumeral 28A. As can be seen in FIG. 2A, the diameter of the pull wire 32is slightly reduced in a portion that lies radially inside the steelband 26B in order to accommodate the reduced inner diameter portion ofthe sheath 14. The outer diameter of the steel bands 26A, 26B is eitherequal or greater than the outer diameter of the sheath 14. The steelbands 26A, 26B are swaged onto the material of the sheath 14, but othermethods of fixing the steel bands to the sheath are contemplated aswell, such as gluing, crimping etc.

The bands 26 a, 26 b may not necessarily be made of stainless steel.Other materials include polymers, such as PHYNOX™, titanium, shapememory alloys, such as NITINOL™. The use of NITINOL™ may be advantageousin that the crimping down of the sheath to a reduced diameter at theposition of the bands may occur upon exposing the catheter to atemperature change, such as by inserting it into the body of a human oran animal. The bands may also be made of radiopaque material so as toserve as marker bands. It is conceivable that the reduced inner diameterportion proximal of the annulus 28 may be provided by a tube heat-shrunkonto the luminal surface 24 of the sheath 14 at the location of thesteel band 26B in order to effect reduction of the inner diameter of thesheath.

The inventors of the present invention have discovered that reducing theinner diameter of the sheath 14 proximal of the annulus 28 isadvantageous in that the sheath can be allowed to remain freelyrotatable with respect to the inner structure of the delivery systemthat effects proximal withdrawal of the sheath. Furthermore, the tensilestrength of the sheath in the proximity of the annulus 28 remainsunchanged due to the constant wall thickness of the catheter sheath inthe proximity of the annulus 28.

It is to be noted that, upon proximal movement of the annulus 28 due topulling the shaft tube in proximal direction, the annulus 28 abuts thereduced inner diameter portion of the sheath 14 at the position of thesteel band 26B, thus effecting proximal withdrawal of the sheath 14 torelease the stent at the distal end portion of the sheath 14.

Furthermore, it is conceivable to provide an annular band, or othermeans, on the luminal surface of the sheath 14 proximal of the annuluswhich restricts proximal movement of the annulus upon pulling action onthe pull wire 32.

A second steel band 26A is provided distally of the annulus 28 on theabluminal surface 24 of the sheath 14. This steel band 26A takes up thepush forces during advancement of the catheter device to the stentingsite. The same considerations apply to the steel band 26A, as previouslydescribed with respect to the steel band 26B.

In any event, any of the above described means for reducing the innerdiameter of the sheath proximal of the annulus 28 must withstand theproximally directed forces when the annulus abuts on the reduceddiameter portion when pulling proximally on the pull wire 32, and thusthe sheath 14.

FIG. 2A further depicts a pusher-guider tube 42 which is arrangedside-by-side with the distal end 50 of the pusher tube 52 of thecatheter device which extends all the way to the proximal end of thecatheter device. The pusher tube 52 is conveniently provided as aPHYNOX™ or stainless steel hypo tube.

As shown in FIG. 2A, the pusher-guider tube 42, in a portion of itslength between its distal end (not shown) and its portion at which thepusher-guider tube 42 is arranged side-by-side with the distal end 50 ofthe shaft pusher tube 52, exhibits slits through the wall thickness ofthe pusher-guider tube 42. These slits are preferably arranged in ahelical string along the axial length of the pusher-guider tube 42. Theyare discontinuous, that is, discrete from one another, so that,typically, each slit in the string extends approximately two completeturns around the longitudinal axis of the pusher-guider tube 42. Theportions of solid material, between each two adjacent spiral cuts in thehelical string impart the pusher-guider tube 42 with sufficienttorqueability in both senses of rotation of one end of the pusher guidertube relative to its other end.

These spiral cuts are preferably made by a laser, but other methods forcutting the slits are conceivable, such as erosion cutting etc.

Of course, the cuts can be arranged on the outer surface, and throughthe wall thickness of the pusher tube in other patterns, such as asinusoidal pattern, helical pattern with varying pitch,circumferentially offset double or multiple helical or sinusoidalpatterns, a pattern of cuts with finite length in which the cuts extendperpendicular, or slightly inclined to the long axis of thepusher-guider tube and in which axially adjacent cuts arecircumferentially offset, etc. The spiral cut arrangement may be adouble- or multi-helix design in which at least the second helix iscircumferentially offset by 180° relative to the first helix.

Any pattern is conceivable which maintains sufficient axial stability oris able to accommodate compressive forces along the long axis of thepusher-guider tube 42 and yet renders the pusher-guider tube 42sufficiently axially elastic or bendable, yet with enough torqueability.

The skilled person may select such slit patterns from stent designs thatexhibit good axial elasticity and bendability, sufficient endwisecompression resistance and sufficient torqueability. In other words, forthe present invention, the slit pattern applied to the pusher-guidertube 42 is to be selected such that its bendability is increased, andthe restoring forces causing the pusher-guider tube to assume itsoriginal shape, i.e. from a curved configuration when advancing it alonga tortuous vessel to a straight configuration, are minimised (consistentwith structural integrity).

Preferably, the width of the laser cut slits and the selected pitchdesign is such that axial deflection of the pusher-guider tube 42 iseffected with minimal or virtually zero amount of force. The wallthickness of the pusher-guider tube 42 is preferably selected such thatthe radiopacity of the stent is not compromised. For that reason thewall thickness of the pusher-guider tube 42 is substantially less thanthe wall thickness of the tubular stent to be delivered by thecatheter-based delivery system.

The inner diameter of the pusher-guider tube 42 is typically at least1.0 mm, and the outer diameter is typically 1.1 mm or more. The innerdiameter and the outer diameter of the pusher guider-tube 42 is selectedto provide, on the one hand, a sufficient gap between a guide wireextending through the lumen of the pusher-guider tube 42, thus reducingthe likelihood of adhesion of the guide wire to the luminal surface ofthe pusher-guider tube 42, and, on the other hand, a sufficient gapbetween the abluminal Surface of the pusher-guider tube 42 and theluminal surface of the stent.

The above mentioned properties may even be achieved by changing thecomposition of the material, used for the pusher-guider tube 42 alongits length. Moreover, the pusher-guider tube 42 may be made of athin-walled stainless steel tube, or a stainless steel hypotube, whichhas been exposed to a thermal treatment process such to exhibit a 40%elongation at fracture, or greater at body temperature.

For achieving the above described properties, the pusher-guider tube 42may be made of a thin-walled stainless steel tube that is fully orpartially annealed. It is preferred that the annealing of variousportions along the axial length of the pusher-guider tube 42 is suchthat the resistance of the portion radially inside the stent to bendingis substantially less than the bending flexibility of the stent itself.Either a thin-walled stainless steel tube fully annealed to exhibit a40% elongation at fracture, or greater at body temperature, or athin-walled stainless steel tube fully or partially annealed andcomprising non-continuous spiral cuts with varying pitch, or athin-walled stainless steel tube not being annealed and havingnon-continuous spiral cuts with varying pitch, may be used for theportion of the pusher-guider tube 42 proximal of the stopper abuttingthe implant. Either the full axial length of the pusher-guider tube maybe subjected to a heat treatment process, or only axial portionsthereof.

The pusher-guider tube 42 can have different lengths. Although not shownin FIG. 2A, the pusher-guider tube 42 may extend beyond the distal endof the stent, or it can terminate at the stopper 40 for abutting thestent, as described below, and connected to a polymer tubing distally ofthe stopper 40. The connection may be established by various means, suchas heat-shrinking a sleeve over the connecting portion, overmolding,gluing, etc.

The pusher annulus 40, as shown in FIG. 2A, comprises two parts.However, it is conceivable that it may comprise more than two parts. Theproximal part 40B is made of metal, preferably stainless steel, such as1.4301 or 1.4305 stainless steel, and is welded at its proximalchamfered end to the pusher-guider tube 42, as indicated by referencenumeral 40C. However, the proximal metal part may be alternatively gluedto the pusher-guider tube 42. The distal part 40A of the pusher annulus40 is made of a polymer which is stiff enough to withstand the forcesexerted by the abutting stent when proximally withdrawing the outersheath 14. The polymer part 40A is preferably overmolded to the steelpart 40B, however, other ways of connecting the polymer part 40A to themetal part 40B are conceivable.

As shown in FIG. 2A, a mechanical engagement interference fit isprovided at the abutting portion of the polymer part 40A and the metalpart 40B. The recessed portions of the polymer part 40A and the metalpart 40B are not restricted to the shape as shown in FIG. 2A. Otherinterference fit designs are conceivable so long as dislodging of thepolymer part 40A from the metal part 40B is prevented.

The polymer part 40A has preferably a length equal to or greater than 2mm. The polymer part 40A due to its non-radiopacity gives good contrastto the metal stent when monitoring the advancement of the catheter-baseddelivery system to the stenting site by X-ray monitoring equipment. Itis also conceivable that the polymer part 40A may have different lengthsin order for the same delivery system to accommodate different lengthsof stents.

The heterogeneous radiocapacity helps to make the stent visible duringintraluminal advancement, that is to say, to provide a material adjacentthe stent that has a radiopacity which is different from that of thestent material. This helps in imaging the stent, and in identifying theposition of the proximal end of the stent during intraluminal delivery.

With reference to FIG. 2 and FIG. 4, we will now explain the structureof the pusher tube extension, distal of the pusher annulus 40, andlocated between that annulus and the end orifice 58 at the distal end ofthe sheath 14.

The metal pusher tube 42 extends for a short distance distally of thepusher annulus 40. A distal extension inner catheter 68 of polyimideabuts the distal end of the pusher tube 42 and is secured to that pushertube by a shrink tube 70 radially overlying the distal end of the pushertube 42 and the proximal end of the inner catheter 68. This shrink tube70 is of PET (which shrinks radially downward to grip both theseabutting portions).

FIG. 4 shows the distal end 72 of the distal extension inner cathetertube 68 and a bore 69 within it, open to the distal end of the innercatheter 68, and terminating proximally at an end-to-end butt joint withthe distal end of the metal pusher tube 42. A tip extension catheter 60of PEBA polymer (PEBAX®) receives the distal end 72 of the innercatheter 68, so that its proximal end 67 overlaps the abluminal wall ofthe catheter 68. Around the distal end 72 of the catheter 68, andsandwiched between the distal catheter 68 and the proximal end zone ofthe tip catheter 60, is a second radiopaque metal marker band 74, andthe whole assembly is bonded together with a cyanoacrylate adhesivecomposition. The PEBAX tip extension catheter 60 extends into thetapered lumen of the taper 16 of the distal end of the sheath 14.

Of note is that the bore 75 of the catheter 60 is contiguous and smoothwith the bore 69 of the catheter 68 for smooth progress of a guidewire.Catheter 60 is soft and floppy but has a larger outside diameter thancatheter 68, which helps to ease the end orifice of the sheath 14 openwhen it begins to withdraw. Proximal end 67 of catheter 60 is taperedinwardly. This is because, should a physician decide to sheath thedistal end of the delivery system after stent deployment by re-advancingthe sheath distally, the tapered tip 16 of the sheath is required toadvance distally back onto the abluminal surface of catheter 60 and thetaper 67 helps that advance.

Reverting to FIG. 2, fixed to the lumen surface of the sheath 14, justproximal of the tapered tip zone 16, is a third radiopaque metal markerband 76 and it will be seen that this marker band lies radially outsidethe second marker band 74 within the distal extension inner catheter 68.

To deploy the stent, the pull wire is pulled by an actuator at theproximal end of the system. A suitable actuator is described below, aspart of a catheter-based delivery system illustrated herein.

In use, the distal end zone of the catheter system, as shown in thedrawings, is advanced along a bodily lumen to a stenting site. When allis ready for deployment of the stent 10, an endwise tension is appliedto the pull wire 32, while the proximal end of the shaft tube 52 isrestrained from endwise movement, reactive or otherwise. Endwisetranslation of the pull wire 32 results in proximal movement of thesheath 14. Holding the endwise position of the shaft tube 52 holds theendwise position of the pusher annulus 40 which in turn prevents anyproximal movement of the stent 10 with the proximally withdrawing sheath14.

Progressively, the sheath 14 withdraws proximally relative to the stent10, having the effect of stretching the distal tip 16 of the sheath 14over the radially outward surface of the stent 10, leading toprogressive release and radial expansion of the stent 10, from itsdistal end toward its proximal end.

Note that, before there is any relative movement of the sheath 14 andpusher annulus 40, the radiologist “sees” only two marker bands, namelythe first marker 40 and the radially superimposed second and thirdmarker bands 74 and 76. However, once the sheath 14 starts to withdrawproximally, the radiologist can see the third marker, at a positionproximal of the second marker. Clearly, when the third marker has movedproximally to approach, pass over, and then move proximally away fromthe first marker 40, one has confirmation that the stent 10 has beendeployed, by full proximal withdrawal of the sheath 14.

During proximal withdrawal of the sheath 14, it will be appreciated thatthe proximal end 18 of the sheath 14 slides proximally over the outsidesurface of the shaft tube 52.

It will appreciated that there should be no endwise movement of theshaft 52 relative to its surrounding entities, whether a bodily lumen orthe lumen of a guide catheter, during deployment of the stent 10. Thisis an opportunity for enhancement of precision of the placement of thestent, because any friction between the outside surfaces of the shafttube 52 and the surrounding structures will only tend to confirm thelocation of the pusher annulus with respect to the body of the patient,and thereby the location of the stent 10 with respect to the body of thepatient.

Further, the friction forces between the pull wire 32 and the luminalsurfaces of the shaft tube 52 ought to be very small or minimal, asshould any frictional forces between the withdrawing sheath 14 and theoutside surface of the shaft tube 52, at the proximal end 18 of thesheath. Further, as the sheath 14 is relatively short in proportion tothe catheter device as a whole, any friction between the outsidesurfaces of the sheath 14 and the surrounding bodily tissue ought alsoto be usefully smaller than in conventional systems where the fulllength of the stent deployment catheter must be moved relative to itssurroundings. All of this elimination of unwanted and unhelpful frictionis advantageous to the person deploying the stent, because any tactilefeedback should relate more closely to events at the stent itself, andany force input at the proximal end of the device should be morecompletely delivered to the components around the stent 10 at the distalend of the device. There should be less lost motion in the systembetween the proximal and distal ends, less hysteresis, and lessdiscrepancy between the amount of force applied at the proximal end andthe amount of force delivered to the components surrounding the stent.It should be possible, with the system proposed herein, to enhance theposition of stent placement, and the degree of confidence that usershave when deploying stents, that the stent has been deployed smoothlyand correctly.

As to design variations, the following will be evident to those skilledin the art, but so too will many more design possibilities, within therelevant published state of the art but not mentioned here.

The sheath need not include braiding. The pull wire can be threadeddirectly to the braiding, thereby avoiding the need for any pullingannulus between the pull wire and the sheath. Neither the distal end northe proximal end or the sheath need be tapered. An atraumatic tip to thedevice can be carried on the pusher sub-system that includes the stentstopper.

Implants to be delivered by the device need not be stents and stentgraft. For example, filters can be deployed with the device.

Those skilled in the art will appreciate how to build an actuator forthe proximal end of the device. A suitable basis is the device describedin WO 02/087470, modified to accommodate the radial inversion of thepush/pull elements.

FIG. 5 is a general view from the side of a catheter-based deliverysystem 200, which, for a self-expanding stent 201, has a distal end 202that advances over a guidewire 204, with the guidewire proximal endadvancing proximally along a guidewire lumen 203 as far as a chosen oneof two alternative guidewire exit ports 206, 208 both distal of theproximal end 210 of the shaft of the catheter 212 of the system. A handunit 214 includes a first actuator 216 and second actuator 218 that canbe used alternatively or sequentially to pull proximally a sheath 220that radially overlies the self-expanding stent at the distal end of thesystem. At a port 222 in a proximal hub 224, flushing liquid can beintroduced, to flush the system of air bubbles. A swivel nut 226connects the catheter shaft 212 to the hand unit 214 to allow the handunit to rotate freely around the long axis of the shaft.

Distal of the hub 224, the catheter shaft is defined by a flushingsleeve 228, which extends distally to a guider block 230 which definesthe more distal of the two alternative guidewire exit ports 206. Distalof the block 230 and proximal of the stent sheath 220 is a PET bellowssleeve 232 that is contiguous with both the flushing sleeve 228 and thestent sheath 220. As the stent sheath 220 is pulled proximally, it getscloser to the adaptor 230, and the bellows sleeve 232 can undergo areduction in length to accommodate this proximal movement. An adhesivesuch as DYMAX® is used to secure the bellows sleeve to the flushingsleeve.

The guidewire port is conveniently located away from both ends of thecatheter system. possibly about half way along the length, or around 75cm from the distal tip of the system.

Turning to FIG. 6, we see that the stent is provided at each end with aring of tantalum marker spoons 234 (see Applicant's WO2002/015820). Thesheath 220 confining the stent is of PEBA polymer (PEBAX®) reinforcedwith a braid of flat stainless steel wire at 45 or 65 pitches per inch,0.13 or 0.075 mm wide and 0.025 mm thick and it has a liner of PTFE(TEFLON®). The sheath has a platinum/iridium marker band 236 embeddedwithin it and overlying the distal end of the stent. Distal of themarker band is a tapered distal tip 238 made of a softer grade of PEBA.The proximal end of the sheath is surrounded by a stainless steelstepped swaged band 239 that presses the sheath 220 inwardly down over ashoulder 237 on a stainless steel pull ring 235 that is welded to thestainless steel, PTFE-coated pull wire 32. The swaged band also pressesonto the pull ring the distal end 241 of a telescope tube 240, andshrunk down onto the radially outer surface of the swaged band is thedistal end 242 of the bellows sleeve 232.

The pull wire enters the distal end 244 of a PHYNOX pusher tube 246, towhich is glued (DYMAX®) a PEBA pusher adapter block 248, FIG. 7, whichdefines two lumens side-by-side, one (250) for the pusher tube and theother (252) for a pusher guider tube 254 which defines the guidewirelumen 203. The pusher-guider tube is made of a closed turn spiral offlat stainless steel wire 0.09 mm thick and 0.25 mm wide with a lumendiameter of 0.95 mm. The outside diameter is ground down to 1.07 mm forthe section of its length that lies within the stent lumen 256. Thepusher-guider tube is co-axial with the catheter shaft from the distaltip 238 of the system until the pull ring 235. Just distal of the pullring, the spiral carries on its radially outside surface a pusher ring260 which faces the ring 234 of spoons at the proximal end of the stent.The pusher ring can be a simple stainless steel ring, or a composite ofa stainless steel ring proximally adjacent a ring of polymer such asPEEK to abut the stent. The outside diameter of the pusher ring in thisembodiment is 2 mm, that is, 6 French.

Proximal of the pull ring, the pusher-guider tube veers through a gentledouble bend to resume a straight line axial course parallel to the pullwire, and as far as the adapter block 248 to which it is fixed in theblock lumen 252 with an adhesive (DYMAX®).

Looking now at FIG. 8, the telescope tube 240 is of polyimide, addsstiffness to the portion of the shaft length that it occupies, andslides over the outside cylindrical surface 249 of the adapter block 248in a proximal direction, when the stent sheath is pulled proximally torelease the stent. The telescope tube in its proximal movementapproaches (but does not abut) the PEBA guider block 230 that is mounted(e.g. by DYMAX® glue) to the pusher tube 246. It is located in thisembodiment about 75 cm from the distal tip of the catheter. The guiderblock, see FIGS. 9 and 10, defines two lumens side-by-side, one (262)for the pusher tube and the other (264) for the guidewire. It has achamfered distal face 266 that helps to steer the proximal end of theguidewire into the lumen during back-loading of the guidewire.Analogously, its proximal-facing end wall 267 is also inclined. Itcarries on its outside cylindrical surface 268 the flushing sleeve 228and over that sleeve is a PEBA band 270 that squeezes the sleeve 228onto the block surface 268, and the block material each side of lumen262 onto the pusher tube within lumen 262. Just proximal of the block isan aperture (not visible) in the flushing sleeve 228 that receives apolyimide guidewire steering tube 272 for leading the guidewire out ofits lumen in the catheter shaft at the distal exit port 206. If the userchooses not to use this exit port, the steering tube 272 is simplypulled away from the system. The side hole left behind in the wall ofthe flushing sleeve is closed by a thin PEBA shrink sleeve 274 thatoverlies radially the flushing sleeve where the steering tube exit holeis found. Absent the steering tube, the guidewire may continue toadvance proximally within the flushing sleeve and alongside the pushertube 246. The flushing sleeve has a distal end somewhat distal of theguider block 230. It receives within its distal end opening 276,telescopically, the proximal end 278 of the telescope tube 240. It is ofpolyimide. The bellows sleeve is glued to the flushing sleeve at anoverlap 279, as mentioned above.

In a first variant, the telescope tube could be radially outside theflushing sleeve.

In a second variant, the flushing sleeve can be integral with thebellows sleeve, thereby obviating the need for any telescopicarrangement.

Following proximally the shaft of the system to the more proximal of thetwo alternative guidewire exit ports brings us to FIG. 11 in which wesee the flushing sleeve ending proximally in a polyamide hub 224 throughwhich the pusher tube 246 continues on proximally. A stainless steelwedge piece 280 is provided in a guidewire lumen 282 of the hub to steerthe proximal end of the guidewire through the hub and out of its exitport 208. Communication with the guidewire lumen and flushing sleevelumen is the flushing port 222 with female Luer lock connector portion284.

Moving on to FIGS. 12, 13 and 14, the pusher tube ends proximally in thepolyamide swivel nut 226 that is mounted to the housing 290 of the handunit 214. Thus, axial movements of the housing relative to the bodilylumen in which the delivery system lies will be transmitted from thehousing to the pusher ring 260 via the push tube 246, to move the stentaxially within that lumen. The pull wire is attached by a brass nipple292 (FIG. 12) or by a loop 294 (FIG. 13) to a polyamide slider 216 (FIG.14) which is the first actuator of the hand unit. The slider 216 runs ona pair of stainless steel rails 296 mounted to the housing, wherebypulling the slider on the rails pulls the pull wire relative to theswivel nut thereby pulling the stent sheath proximally.

But the slider 216 is on the distal end of a pulling line 298 which iswound up on a drum 300 journalled in the housing. Each pump on a trigger218 causes a toothed rack piece 302 to advance in engagement with theteeth of a toothed wheel 304 on the drum, and a pawl stops any reversemovement of the toothed wheel and drum during return movement of therack 302 and trigger 218 after each squeeze of the trigger. The returnmovement is induced by a return spring 308, the bias of which has to beovercome during each squeeze of the trigger. Thus, the stent can bereleased by a succession of squeezes on the trigger, or by one longsmooth proximal stroke of the slider, or by any combination of these twoactuators (see Applicant's earlier WO2002/087470).

It will be appreciated that the illustrated embodiments, and theinvention as claimed, make available a system to deploy a self-expandingstent, or other implant, that has a number of valuable advantages,including:

i) no axial movement of the outer surface of the shaft of the deliverysystem relative to surrounding bodily tissue during stent deploymentii) long thin load-bearing components entirely of metal, for bothco-axial parts of the stent release system, so minimising length changeswhen the shaft length is suffering the endwise stresses that are imposedon it when the stent sheath is being pulled proximally off the stentiii) the tolerance of different stent lengths and diameters that flowsfrom a design that is inherently modular (see Applicant's WO2003/003944)iv) choice of two different lengths of guidewire lumenv) an absence of re-entrant surfaces on the tip of the system inside thestent lumen, so that withdrawal of the system after deployment of thestent should not carry the risk of dislodging or parting bodily tissuefrom the stenting site as the tip withdraws proximally through the stentlumen (see Applicant's WO2001/034061).

The system illustrated in FIGS. 5 to 14 has been described with diameterdimensions. It will be appreciated that these dimensions can all bemodified, more or less in proportion, to create other systems with arange of different overall diameters.

A number of published documents have been mentioned above. Many of theseare from Applicant, and represent steps along the way to the presentinvention. It is intended that the disclosures of these earlierdocuments are incorporated by these references into the teaching anddisclosure of the present specification.

1. A catheter device having a shaft that extends from a proximal end toa distal end to carry on its distal end a self-expanding implant forintraluminal advance on a guidewire and delivery of the implant to animplant site by proximal withdrawal of a sheath that lies radiallyoutside the implant in the catheter, the catheter including a firstshaft element to pull the sheath proximally and a second shaft elementto push the implant distally to prevent the implant moving proximallywith the sheath when the sheath is pulled proximally, wherein the secondshaft element comprises a pusher-guider tube having a wall thicknesswith a plurality of discrete slits, the slits extending through the wallthickness of the pusher-guider tube.
 2. Catheter as claimed in claim 1,wherein the slits are arranged in a helical string on the outer surfaceand along the axial length of the pusher-guider tube.
 3. Catheter asclaimed in claim 2, wherein the helical arrangement of the slits formsmore than one spiral along the length of the pusher-guider tube. 4.Catheter as claimed in claim 2, wherein there is at least as manydiscrete slits in the helical string as there are pitches in saidhelical string.
 5. Catheter as claimed in claim 2, unslitted materialbetween adjacent slits of the string being located on a line parallel tothe long axis of the pusher-guider tube.
 6. Catheter as claimed in claim5, wherein the slits are arranged in two helical strings, each with itsown line of unslitted material, and the respective lines associated witheach of the two strings are 180° apart on the circumference of thepusher-guider tube.
 7. Catheter as claimed in claim 6, wherein the pitchof the second helix is the same as that of the first helix.
 8. Catheteras claimed in claim 1, wherein the second shaft element carries astopper for abutting the implant, and wherein the arrangement of slitsis confined to the portion of the pusher-guider tube distal of thestopper.
 9. Catheter as claimed in claim 8, wherein the pusher-guidertube has been heat-treated, and the portion of the pusher-guider tubeproximal of the stopper has a heat treatment history different from thatof the portion distal of the stopper.
 10. Catheter as claimed in claim1, and loaded with an implant, wherein the pusher-guider tube extendsdistally beyond the distal end of the implant.
 11. Catheter as claimedin claim 1, wherein at least an axial portion of the length of thepusher-guider tube is of stainless steel.
 12. Catheter as claimed inclaim 10, wherein the stainless steel tube has an elongation at fracturethat is at least 40%.
 13. Catheter as claimed in claim 1, wherein anaxial portion of the length of the pusher-guider tube is made of apolymer.
 14. Catheter as claimed in claim 1, including a self-expandingstent.
 15. Catheter as claimed in claim 3, wherein there is at least asmany discrete slits in the helical string as there are pitches in saidhelical string.
 16. Catheter as claimed in claim 3, unslitted materialbetween adjacent slits of the string being located on a line parallel tothe long axis of the pusher-guider tube.